Studies On Metal-Semiconductor Contacts Of 6H-SiC And Some Interrelated Processes

Studies on Metal-Semiconductor Contacts of 6H-SiC and some interrelated ProcessesCondensed-state PhysicsPostgraduate: Wu Ruibin Director: Gong Min The manufacturing processes as well as electrical and thermal characters of 6H-SiC ohmic contacts have been studied in this work. In addition, we fabricated Au and Ni Schottky Barrier Diodes (SBDs) on Silicon surface of n-type 6H-SiC. Ohmic contacts on H2-thermally-treated 6H-SiC surface by evaporating aluminum without annealing have contact resistances of 8 10-3 -cm2 on room temperature and keep fairly good thermal stability under the temperature of 400 . Its ohmic properties don't depend on the doping concentrations of the substrate, which enables us to form ohmic contacts on low dropped substrate especially on epitaxial layer. XPS study shows the mechanism that ohmic properties of the contacts become worse is commutative difiusion between aluminum and silicon in 6H-SiC. Ni ohmic contacts fabricated by traditional evaporation and thermal annealing on temperature of about 1000 have lower contacts resistances .The testing result on 400 doesn't show it can keep thermal stability. Au and Ni/6H-SiC SBDs fabricated by metal overlap edge silicon dioxide termination have good forward current-voltage (I-V) characters but not anticipative reverse characters. At room temperature, Au/6H-SiC SBD has ideal factor of 1.75, effective barrier height of 1.39eV, threshold voltage of 0.9V and reverse breakdown voltage of 120V. At forward bias of 2V, the diode has a current of 66.4A/cm2. Ni/6H-SiC SBD has ideal factor of 1.71, effective barrier height of 1.21eV, threshold voltage of 0.85V and reverse breakdown voltage of 310V. At forward bias of 2V, it has a current of 85.3A/cm2. All diodes have large reverse leak current density, which maybe caused by some reasons such as many ions are brought in course of evaporating metal on silicon surface of 6H-SiC, chemical etch brings disfigurements such as burrs and dentate erodes as well as the rinse on surface of samples is not drastically accomplished.